In the manufacturing of semiconductor devices, a variety of joining materials are used in order to join a semiconductor element and a lead frame or the like (supporting member). High-melting-point lead solders have been used as a joining material for the joining of, among semiconductor devices, power semiconductors, LSI, and the like that are operated at a high temperature of 150° C. or higher. In recent years, an increase in the capacity of semiconductor elements and the energy-saving trend have increased the operation temperature to near the melting point of high-melting-point lead solders, which has made it difficult to ensure connection reliability. On the other hand, in association with the tightening of RoHS regulations, there has been a demand for joining materials containing no lead.
Hitherto, the joining of semiconductor elements using a material other than lead solders has been studied. For example, Patent Literature 1 proposes a technique for forming a sintered silver layer by sintering silver nanoparticles. Sintered silver as described above is known to have high connection reliability with respect to power cycles (Non Patent Literature 1).
Regarding a different material, a technique for forming a sintered copper layer by sintering copper particles is also proposed. For example, Patent Literature 2 discloses a copper paste for joining including copper (II) oxide particles and a reducing agent as a joining material for joining a semiconductor element and an electrode. In addition, Patent Literature 3 discloses a joining material including copper nanoparticles and copper micro particles and/or copper submicro particles.